Heteropoly acids are a class of acids generally characterized by a combination of hydrogen and oxygen with certain metals and non-metals. Heteropoly acids and their conjugate polyoxometalate anions are commonly known for their strong Brønsted acid character, oxidative capacity, catalytic activity, and conductivity. The chemical diversity of the heteropoly acids and their conjugate polyoxometalate anions allow for a wide variation in chemical and physical properties. The chemical and physical properties of heteropoly acids and their conjugates are well suited for fuel cell and supercapacitor electrode applications.
The use of fuel cells to produce electrical energy has been known since the nineteenth century. However, commercial use of fuel cells as a source of power was eclipsed by inexpensive, readily available fossil fuels. The use of fuel cells as a power source was renewed when a clean, reliable, and compact source of electrical energy was needed for satellites and spacecraft. Fuel cells are being considered again as an energy source as the global community faces diminishing fossil fuel reserves and environmental concerns related to their use. Fuel cells typically generate power more efficient and cleaner than fossil fuel combustion.
Fuel cell technology is diverse and varied encompassing, but not limited to: boron hydride, protonic ceramic, solid state, molten carbonate, metal hydride, polymer electrolyte membrane, proton exchange membrane, and solid oxide fuel cells. Polymer electrolyte membrane hydrogen fuel cells utilize carbon supported platinum catalysts which suffer from: poor long term durability, due to the platinum being an inefficient catalyst that produces hydroxyl and peroxyl radicals that decompose the polymeric electrolyte membrane; the dissolution of platinum at high fuel cell electrode potentials; high activation over-potentials; high cost, due to required platinum loading levels; and poor carbon monoxide tolerance which hinders fuel cell performance. The major pathway for membrane decomposition arises from dissolved platinum particles that deposit within the membrane that function as a catalyst for the generation of peroxyl and hydroxyl radicals.
FIG. 1 depicts a single cell 101 of a typical polymer electrolyte membrane hydrogen fuel cell. The typical fuel cell comprises one or more cells 101 “stacked” or layered. Generally, the greater the number of layers, the greater the electrical power generated by the fuel cell.
Fuel cells and batteries are similar; both produce electrical power by electrochemical means: the fuel cell produces power continuously as long as reactants are supplied. While, the battery produces power for a finite period of time determined by the quantity and type of reactants contained within the battery.
Hydrogen 139, supplied as molecular hydrogen H2 gas, enters cell 101 between anode 115 and anodic bipolar plate 131. At the anode 115 the hydrogen 139 is oxidized, the products of that half-cell oxidization are electrons 147 and protons 107. Within a complete (i.e., closed) electrical circuit, the electrons 147 flow to a power draining source 155 and the hydrogen protons 107 migrate through a proton conductor electrolyte 103 to cathode 119, where the protons 107 react with oxygen 127. Within a polymer electrolyte membrane fuel cell the electrolyte 103 comprises a polymeric electrolyte membrane. Typically, the polymeric electrolyte membrane has a noble metal catalyst (commonly, platinum) to assist in the electrochemical half-cell reactions at least one of the anode 115 or cathode 119. A gaseous mixture containing the oxygen 127 enters the cell 101 between the cathode 119 and cathodic bipolar plate 135. The protons 107, oxygen 127 and electrons 147 are components of the reductive cathodic half-cell reaction which forms water 161 and heat 165.
A capacitor is another device which functions like a battery. While both the battery and capacitor provide energy by discharging electric charges, the battery stores the electrical energy as chemical energy and the capacitor stores the electrical energy directly as electrical charges. The common components of a typical capacitor 200 are depicted in FIG. 2. The typical capacitor 200 comprises first 201 and second 202 conductors separated by a gap 203. The first 201 and second 202 conductors can be substantially similar or differ, typically they are substantially similar. The gap 203 can comprise a void or dielectric. Examples of suitable dielectrics are paper, plastic, mica, ceramic, electrolyte, and glass.
A supercapacitor, also known as an ultracapacitor or electrochemical double layer capacitor, is capable of storing large quantities of electrical charges. The typical capacitor stores about a microfarad of charge (that is, 10−6 farads), while the supercapacitor stores up to about 1,000 farad (that is, 103 farads) or more. The supercapacitor has commercial applications for replacing batteries due to their quick charging and discharging capacities, temperature stability, and excellent safety and environmental characteristics.
As used herein, “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.
It is to be noted that the term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably.
The process and methods disclosed within the subject invention address these limitations.